Understanding Multimodal Accessibility Parameters in Diverse Urban Environments: a Pilot Study in Darmstadt
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Lakshya Pandit & Martin Knöll, Int. J. Transp. Dev. Integr., Vol. 3, No. 4 (2019), 317–330 UNDERSTANDING MULTIMODAL ACCESSIBILITY PARAMETERS IN DIVERSE URBAN ENVIRONMENTS: a piloT STUDY IN DARMSTADT LAKSHYA PANDIT & MARTIN KNÖLL Urban Health Games, FB15, TU Darmstadt, Germany ABSTRACT The research takes into consideration diverse perspectives and parameters for assessing accessibility in urban spaces within the Frankfurt Rhein-Main Area, with the initiation of pilot study in Darmstadt, being one of the major cities forming the urban agglomeration. Diverse tools including public transport accessibility level and Space Syntax which contribute to the factor of accessibility are studied and uti- lized in different urban spaces and further correlated. The study takes into consideration the city centre, the main transit station and a residential area, as three urban spaces within Darmstadt, to understand how the selected performance measures quantify leading to qualitative learning and inferences. The study aims to further evolve in future stages, in order to understand the diversity through the acces- sibility performance measures through different cities, based on commuter flows, within the urban agglomeration. Assessing accessible mobility in continuum within the urban agglomeration, through interdisciplinary means of research methodology, would assist in the vision (as per German legislation) of obtaining an accessible and integrated multimodal transport system by 2022. Keywords: accessibility, agglomeration, mobility. 1 INTRODUCTION In an urban environment, majority of trips include a sequence of travel modes in order to reach a destination. A multimodal transportation system allows people to use a variety of transportation modes, including walking, biking and other mobility devices, as well as transit where possible. These modal integrations may differ in their functional capacities, in con- tinuum, in different urban environment. Such a system reduces dependence on automobiles and encourages more active forms of personal transportation, improving health outcomes and increasing the mobility of those who are unable or unwilling to drive [1]. The research tends to identify the state of the art benchmarking accessibility tools, in order to study the multimodal accessibility within urban agglomerations. The study is pri- oritized on the urban agglomerations with strategic vision towards obtaining an objective of enhanced mobility in future. With respect to the strategic vision of Mobiles Hessen 2035, the short-distance mobility must again be the basis of mobility for cities and towns [2], with Frankfurt Rhein-Main region being one of the major urban agglomerations within the state of Hessen. According to regional planning definition, FrankfurtR hein-Main Metropolitan region includes seven independent cities of Frankfurt am Main, Offenbach am Main, Wies- baden, Mainz, Worms, Darmstadt and Aschaffenburg, along with 18 counties. The cities lend the region its metropolitan character, a polycentral city system held together with a strong network. As per the 2018 data, the commuter flow within the Frankfurt Rhein-Main region shows the major cities, including Wiesbaden, Offenbach, Mainz and Darmstadt, which contribute towards the major mobility share in the region. Majority of these com- muter flows are directed towards the city of Frankfurt within the Hessen state.T he cities dominant with the commuter flows in the urban agglomeration fell within the urban districts © 2019 WIT Press, www.witpress.com ISSN: 2058-8305 (paper format), ISSN: 2058-8313 (online), http://www.witpress.com/journals DOI: 10.2495/TDI-V3-N4-317-330 318 Lakshya Pandit & Martin Knöll, Int. J. Transp. Dev. Integr., Vol. 3, No. 4 (2019) of the state of Hessen, excluding Mainz, which lies within the Rhineland-Palatinate state in the urban district [3]. With the onset of population growth and increase in mobility demands, access and priority of diverse means of mobility, especially short-distance mobility, have to be taken into consideration. 2 uNDERSTANDING ACCESSIBILITY AND ITS PARAMETERS With the onset of ongoing urban studies, defining accessibility within the urban context takes various perspectives. With respect to Engwicht, accessibility refers to the ease of arrival to facilities, activities or goals, which could be appointed in general as opportunities. Accessi- bility could be defined as the intensity of possibility of interaction and exchange [4]. Litman interprets the definition with respect to the profession of the individuals, to which the bound- aries and scope limit itself to. With respect to the land-use planner, geographical accessibil- ity, i.e. distances between activities, is the major focus, whereas for transport planners, more focus is generated upon the mobility aspect [5]. There has been a paradigm shift from conventional mobility planning, which placed auto- mobiles at the nucleus of the transportation system to a more accessible-based planning which places people at the centre of the planning process. Bertolini defines accessibility through a medium of space as a node, with an accessible public space being one where many different people can come and also do many different things [6]. The public space is treated as a central accessible nodal point and also includes the spaces within the node. This approach focuses more upon the diverse human mobility factors with a barrier-free environment, serving as an inclusive space with higher degree of accessibility. The statement also defines that the focal point acts as a node; in other words there are other nodes which act as spaces, which are not necessarily public spaces but other elements like pedestrian junctions, public transportation service stops, etc. Assessing accessibility is often difficult to interpret, and understanding the performance measures which take into account the qualities contributing towards the overall perspective of accessibility is taken into consideration through literature studies (Fig. 1). The measures reviewed were based on the similar boundaries with respect to the micro- and macro-scales, which help in relating the different perspectives of assessing accessibility and understanding the inter-parametrical relations through the urban scenario. The research focuses on under- standing how these perspectives can be utilized in order to understand and improve the acces- sibility paradigm through multimodal mobility. 2.1 Selection of accessibility parameters The research takes into consideration three parameters for the pilot study, through a transi- tion, from a micro- to macro-based perspective, involving modes of travel limiting to public transport i.e. bus, tram, train and pedestrian access. The measures include public transport accessibility level (PTAL), intelligibility and connectivity index. The area of observation for the assessment of the last two parameters is limited within 1 km2. With respect to the PTAL, the 640-m radius limits the study for the bus service stations and 960-m radius limits the study for the rail service stations. These boundaries are based on the comfortable walking timeframe for human limiting to 8 min and 12 min for the services, respectively [7] (Fig. 2). The selected parameters and their perspective with respect to accessibility are discussed in the following sections. Lakshya Pandit & Martin Knöll, Int. J. Transp. Dev. Integr., Vol. 3, No. 4 (2019) 319 Figure 1: State-of-the art measures focusing on accessibility-based paradigm. Figure 2: Accessibility perspectives and observation boundaries within selected parameters. 320 Lakshya Pandit & Martin Knöll, Int. J. Transp. Dev. Integr., Vol. 3, No. 4 (2019) 2.1.1 Public Transport Accessibility Level (PTAL) The methodological index was developed in 1992 by the London Borough of Hammersmith and Fulham. The index takes into consideration the walk access times and the service avail- ability of the transportation modes during the morning peak hours within a predefined zone from a point of interest (poi). Walk times are calculated from specified points of interest to all public transport service access points, i.e. bus stops, rail stations, underground stations and tram stations. For the cal- culation of the walk access time, assumed average human walking speed of 4.8 kph is taken into consideration with respect to the shortest accessible pathway. The walk access time (Twat) along with the average waiting time (Tawt) for the service leads to the total access time (Ttat). The total access time is later converted into equivalent doorstep frequency (EDF), which determines a measure as if the transport service was available at the doorstep. With respect to the maximum frequency of the service, the weightage of 1 is given to the particular route, as compared to the others with 0.5 weightage. The overall process is summed up as follows: Ttat = Twat + Tawt (1) Tawt = [0.5×(60/ƒ)] + r (2) EDF = 30/Ttat (3) The time measure is calculated in minutes for the index, with ƒ denoting the morning peak hour service frequency and r being the reliability factor with respect to late services. The reli- ability factor for bus services is 2 min while that for rail services is 0.75 min [8]. Imode = EDFmax + EDFothers × 0.5 (4) Ipoi = ∑Imodes (5) Overall, the cumulative indexes for each mode is calculated in order to achieve an overall index (Ipoi) value. The indexes are categorized into six levels, with 1 (1a and 1b) being the lowest level of accessibility, with the index value below 5.01 (for 1b), and 6 (6a and